[RUBY] What to do if you get an "A server is already running." Error when you try to start the rails server

When I try to start rails server, I get the following error and may not be able to start it.

$ rails s -b 0.0.0.0
=> Booting Puma
=> Rails 5.2.4.2 application starting in development 
=> Run `rails server -h` for more startup options
A server is already running. Check /Directory path/tmp/pids/server.pid.
Exiting

This is an error that occurs because the server is already running. Here's what to do in this case.

Kill the PID of server.pid

All you have to do is kill the PID number in /tmp/pids/server.pid. Even if I manually delete the server.pid file, the server is still running, so Execute the following command to find and kill the process running on number 3000.

$ lsof -i:3000
COMMAND  PID    USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
ruby2.5 3033 vagrant   16u  IPv4  27499      0t0  TCP *:3000 (LISTEN)

Kill the PID number found by the above command with the following command.

$ kill -9 3033

This will shut down the server and start it fine.

Reference article

https://qiita.com/motty93/items/d22c1eb8f5128f8cd7f8

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